Copper base alloys



Patented July 3, 1951 COPPER BASE ALLOYS John Sykes, Enfield, England, assignor to Enfield Rolling Mills Limited, Enfield, England, a companyof Great Britain No Drawing. Application July 19, 1944, Serial No.

545,720. In Great Britain August 26, 1943 q 8 Claims. (Cl. 75-453) This invention relates to the production of copper-base alloys, and in particular copper-base alloys suitable for use in the manufacture of electrical contacts, electrodes and other components and parts of electrical apparatus requiring high electrical conductivity in conjunction with high strength and resistance to wear at both normal and elevated working temperatures.

Alloys of copper and silver are already well known and have been used for, amongst other purposes, the production of contact electrodes for resistance welding machines, but in practice considerable variation has been met with in the electrical and physical properties of such alloys despite apparent uniformity in the proportions of silver and copper present.

I have found that copper-silver alloys with consistently high electrical conductivity and good and consistent physical properties can be obtained by utilizing a silver content within a given range and including a carefully controlled small percentage of oxygen.

The present invention accordingly consists in a high-duty copper-base alloy, wherein silver or a silver-copper master alloy is added to a copper melt so that silver is present in the final alloy to the extent of from 5% to 7% and the oxygen content is controlled so that oxygenis present to the extent of from 0.04% to 0.1%.

The invention further consists in a high-duty copper-base alloy comprising from 5% .to 7% silver, from 0.04% to 0.1% oxygen and the balance copper.

It is to be understood that impurities normal to commercial copper may also be present, though it is desirable that the presence of arsenic or antimony be avoided as far as is practicably possible.

In practice the best method of controlling the oxygen content within the range named above is found to be by poling after alloying, covering the melt with a layer of charcoal or other dry carbonaceous material without, or low in sulphur, and making periodical microscopic examinations and when necessary, chemical analyses.

Alternatively, the oxygen content may be controlled by the addition to the melt of a suitable de-oxidant such as phosphorus, silicon or lithium, care being taken however to avoid as far as possible any residual of the de-oxidant in the final alloy.

The improved alloy is particularly suitable for the production of contact electrodes for resistance welding machines, and the best results for this purpose have been obtained by casting the alloy in water cooled copper moulds, the rate of flow of the coolant being carefully controlled to give a uniform rate of cooling of the alloy and thereby maintain a very fine and uniform grain size in the casting.

The cast billet is subsequently cooled in air to a temperature lower than the eutectic point of the alloy before finally quenching.

The disc or other part out from the billet is subsequently cold forged prior to final machining, this forging operation imparting a high degree of hardness together with an increase in the electrical conductivity. Typical hardness figures thus obtained are 140-160 V. P. H. An electrical conductivity of 85% has also been obtained consistently.

In some cases, depending upon the amount of change of dimensions to be achieved by cold forging, it is necessary to proceed in stages with intermediate anneals, and such annealing must be carried out in a reducing atmosphere to avoid surface oxidation and the risk of surface cracking, as forging proceeds.

In the production of an alloy for use in the manufacture of disc welding electrodes as used in resistance seam welding, it is preferable to maintain the silver content between the limits 6.2% to 6.5% and the oxygen between 0.045% and 0.055%.

The fabrication of articles from silver-copper alloys by processes involving hot or cold working requires great care owing to an inherent weakness in the grain boundaries due to the formation of the eutectic, with consequent risk of rupture between individual crystals or grains during such fabrication.

As a further feature of the present invention, an addition of from 0.1% to 0.2% of either nickel or cobalt or chromium may be made to the silvercopper, oxygen-containing alloy described above and replacing copper, whereby improved malleability is obtained with further increase in hardness after forging and but slight lowering of the electrical conductivity.

I claim:

1. A high-duty copper-base alloy consisting of from 5% to 7% silver, from 0.04% to 0.1% oxygen and the balance copper.

2. A high-duty copper-base alloy consisting of from 6.2% to 6.5% silver, from 0.045% to 0.055% oxygen and the balance copper.

3. A high-duty copper-base alloy consisting of from 5% to 7% silver, from 0.04% to 0.1% oxygen, 0.1% to 0.2% nickel and the balance copper.

4. A high-duty copper-base alloy consisting of from 5% to 7% silver, from 0.04% to 0.1% oxygen, 0.1% to 0.2% cobalt and the balance copper.

5. A high-duty copper-base alloy consisting of from 6.2% to 6.5% silver, from 0.045% to 0.055% oxygen, 0.1% to 0.2% nickel and the balance copper.

6. A high-duty copper-base alloy consisting of from 6.2% to 6.5% silver, from 0.045% to 0.055% oxygen, 0.1% to 0.2% cobalt and the balance copper.

7. A high-duty copper-base alloy consisting'of from 5% to 7% silver, from 0.04% to 0.1% oxy-v gen, up to 0.2% of a metal-selected. from the group consisting of nickel and cobalt and the balance copper.

8. A high-duty copper-base alloy consisting of from 6.2% to 6.5% silver, from 0.045% to 0.055%

oxygen, up to 0.2% of a metal selected from the group consisting of nickel and cobalt and the balance copper.

JOHN SYKES.

REFERENCES CITED The following references are of record in the -file of this patent:

UNITED STATES PATENTS Number Name Date 1,651,970 Schenck Dec. 6, 1927 1,660,220 De .Golyer Feb. 21, 1923 1,723,922 Corson Aug. 6, 1929 .l,771;977 Blomberg July 29, 1930 1,955,576 Clapp et a1 Apr. 17, 1934 2,073,371 Hensel Mar. 9, 1937 2,143,914 Hensel et a1 Jan. 17, 1939 

7. A HIGH-DUTY COPPER-BASE ALLOY CONSISTING OF FROM 5% TO 7% SILVER, FROM 0.04% TO 0.1% OXYGEN, UP TO 0.2% OF A METAL SELECTED FROM THE GROUP CONSISTING OF NICKEL AND COBALT AND THE BALANCE COPPER. 